Running water was a thing of inner cities until the nineteen sixties, more or less, when it swept the country in a big wave, and many houses were retrofitted. In most places some pantry or part of a hall were adapted into bathrooms, preferrably as close to the kitchen as possible, to save on pipes and labor - the walls are solid, so it takes a lot of digging grooves into them to run the pipes.
This also meant the bathrooms were somewhere to the outer walls, so the sewer wouldn't require digging too much of the floor.
In the end, the bathrooms all had that crammed look, with as many amenities compressed into available space as ingenuity allowed. The water heater was always inside the bathroom. The central heating being still somewhere in the future, most of the bathrooms had a heater of their own, usually a single curved heater bar with a reflector. The washing machines were regularly crammed into the same tiny room, but since they were in unforeseeable future when the bathrooms were built, they were only left one add-on valve on one of the faucets, very rarely a faucet of their own (extra pipes!) and no provision to connect the exhaust to the sewers. The exhaust pipe was usually hung on the toilet bowl, and covered with the seat so it wouldn't jump off when it pumps out the first burst.
Even the novogradnja, the apartment buildings, had such bathrooms - there was no way any space would be taken by such luxury as a separate washroom, where the heater and washer would be, and I don't think the idea crossed anyone's mind.
However, cramming everything into the tiny bathroom had one big exception. Somehow, the technical regulations came to every majstor's head in the part where it said that there would be only minimal electricity in such a wet environment, so all the switches were on the outside. Usually, when you're a guest somewhere, and look for the bathroom, you don't need to ask which door. You look for one that has two stronger switches and two simple light switches next to it. The strong ones, often with a red signal light to them, are for the water heater and the area heater (sometimes there's a third, to cut power to the washer), and the simple ones are for the light and maybe the fan.